The incidence of psychoactive substances and alcohol among impaired drivers in Denmark in 2015-2019.

This study examines the presence of psychoactive drugs and alcohol in blood from apprehended drivers driving under the influence of drugs (DUID) and alcohol in Denmark in a five-year period from 2015 to 2019. Data were analysed with respect to gender, age, substances with concentrations above the Danish legal limit, arresting time of day and repeat arrest. By request of the police, the blood samples were subjected to analysis for alcohol and/or tetrahydrocannabinol (THC) alone, for "other drugs" (covering all drugs including new psychoactive substances (NPS), except THC, listed in the Danish list of narcotic drugs) or for both THC and other drugs. About the same number of alcohol traffic cases (37,960) and drug traffic cases (37,818) were submitted for analysis for the five-year period. The number of drug traffic cases per year increased from 5660 cases in 2015 to 9505 cases in 2019, while the number of alcohol traffic cases per year (average, 7600) was unchanged. Ethanol (89.2%) was the overall most frequent single substance, followed by THC (68.2%). CNS stimulants (46.8%) were the second most prevalent group of non-alcoholic drugs. Cocaine (23.8%) and amphetamine (22.9%) were the most frequent CNS stimulants. The proportion of CNS-stimulant positive drivers more than doubled in ten years. Benzodiazepines/z-hypnotics (12.7%) were the third most prevalent drug group detected, with clonazepam (8%) as the most frequent drug. Opioids were above the legal limit in 9.8% of the cases. NPS was above the legal limit in 128 cases (0.6%). Poly-drug use occurred in 40% of the DUID cases in the requested groups: other drug or other drug/THC. Young males dominated the DUID cases (median age 26). Drink-drivers (median age 39) were also mainly men, but the age distribution was equally spread over the age groups. Re-arrest occurred more often in DUID drivers (18-29%) than in drinking drivers (6-12%). DUID was evenly spread over the week, while drink-driving was most frequent on weekends. This study is an important supplement to the knowledge of drug use in Denmark. It was the well-known psychoactive substances that were detected. Only a few NPS occurred. However, the abuse pattern has changed, and CNS stimulants now account for a much higher proportion than earlier. Our results indicate a drug use problem among DUID drivers. This gives rise to concern because of a risk of traffic accidents. Treating the underlying abuse problem is therefore recommended, rather than focusing solely on prosecuting.